Abnormality determination apparatus for internal combustion engine

ABSTRACT

An abnormality determination apparatus for an internal combustion engine in which an intake passage upstream of a supercharger and a crankcase are connected by a breather line includes: an intake flow rate detection unit that detects an intake flow rate in the intake passage; and an abnormality determination unit that determines abnormality of the breather line. The abnormality determination unit calculates a rotation second-order component of a fluctuation waveform of the intake flow rate, accumulates a first number of times for which the rotation second-order component exceeds an upper threshold and a second number of times for which the rotation second-order component falls below a lower threshold, and determines the abnormality of the breather line by comparing an accumulated value of the first number of times and the second number of times with the number of revolutions of a crank.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2019-021330, filed Feb. 8, 2019, entitled “Abnormality Determination Apparatus for Internal Combustion Engine.” The contents of this application are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to an abnormality determination apparatus for an internal combustion engine in which an intake passage upstream of a supercharger and a crankcase are connected by a breather line.

BACKGROUND

Such an abnormality determination apparatus for an internal combustion engine is described as a second embodiment in Japanese Unexamined Patent Application Publication No. 2017-078378. In such a case where the connection portion of the breather line to the intake passage has come off, the connection portion serves as an opening end portion for the air column of the intake passage, thus causing the resonant frequency of the air column to change. Focusing on this fact, this abnormality determination apparatus for an internal combustion engine monitors the magnitude of the pulsation of the intake flow rate in the intake passage to determine whether the connection portion of the breather line has come off.

In the above-described conventional abnormality determination apparatus, if the load on the internal combustion engine temporarily fluctuates due to disturbance or the like, the pulsation of the intake flow rate fluctuates to a large extent. For this reason, there is a possibility that the above-described conventional abnormality determination apparatus erroneously determines whether the connection portion of the breather line has come off.

SUMMARY

It is desirable to precisely determine the abnormality of a breather line of an internal combustion engine without being affected by disturbance or the like.

A first aspect of the disclosure proposes an abnormality determination apparatus for an internal combustion engine in which an intake passage upstream of a supercharger and a crankcase are connected by a breather line, including: an intake flow rate detection unit that detects an intake flow rate in the intake passage; and an abnormality determination unit that determines abnormality of the breather line, wherein the abnormality determination unit calculates a rotation second-order component of a fluctuation waveform of the intake flow rate, accumulates a first number of times for which the rotation second-order component exceeds an upper threshold and a second number of times for which the rotation second-order component falls below a lower threshold, and determines the abnormality of the breather line by comparing an accumulated value of the first number of times and the second number of times with the number of revolutions of a crank.

According to the configuration of the first aspect, it is possible to precisely determine the abnormality of the breather line based on the rotation second-order component of the fluctuation waveform of the intake flow rate, which is unlikely to be affected by fluctuation in load on the internal combustion engine due to disturbance or the like.

A second aspect of the disclosure proposes an abnormality determination apparatus for an internal combustion engine in which in addition to the configuration of the first aspect, the rotation second-order component is calculated by multiplying the fluctuation waveform of the intake flow rate by a sine wave and a cosine wave corresponding to an angular velocity of the crank, followed by integration.

According to the configuration of the second aspect, it is possible to easily calculate the rotation second-order component of the fluctuation waveform of the intake flow rate.

Note that an air flow meter 16 in an embodiment corresponds to the intake flow rate detection unit of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages of the disclosure will become apparent in the following description taken in conjunction with the following drawings.

FIG. 1 is a diagram illustrating the configuration of an internal combustion engine including an abnormality determination apparatus for a breather line of one embodiment of the present application.

FIG. 2 is a block diagram of the abnormality determination apparatus for the breather line of one embodiment of the present application.

FIGS. 3A and 3B are explanatory diagrams for change in position of a piston associated with the rotation of a crankshaft of one embodiment of the present application.

FIG. 4 is an explanatory diagram of an approach of determining abnormality of the breather line of one embodiment of the present application.

FIG. 5 describes bandpass filter for extracting only the rotation second-order component from the fluctuation in the intake flow rate in the intake passage.

DETAILED DESCRIPTION

Hereinafter, an embodiment of the disclosure will be described based on FIGS. 1 to 4.

As illustrated in FIG. 1, on an intake passage 12 of an in-line four-cylinder 4-cycle internal combustion engine 11 to be mounted on an automobile, disposed are: an air cleaner 15, which removes dust in intake air; an air flow meter 16, which measures the intake flow rate; a supercharger 17 composed of a turbocharger or a supercharger, which pressurizes the intake air; and a throttle valve 18, which adjusts the intake flow rate by narrowing the intake passage 12, in this order from an inlet 13 at the upstream end in the flow direction of the intake air toward an intake manifold 14 at the downstream end in the flow direction of the intake air. A portion of the intake passage 12 between the air flow meter 16 and the supercharger 17 and a crankcase 19 of the internal combustion engine 11 are connected by a breather line 20. The intake manifold 14 and the crankcase 19 of the internal combustion engine 11 are connected by a positive crankcase ventilation (PCV) line 21, and a middle portion of the PCV line 21 is opened and closed by a PCV valve 22.

Part of the fuel component contained in the intake air flows from the combustion chamber of the internal combustion engine 11 into the crankcase 19 through a gap between a piston and a cylinder as a blow-by gas, which is returned to the intake passage 12 through the breather line 20 or is returned to the intake passage 12 through the PCV line 21. The fuel component contained in the blow-by gas is thus prevented from being released to the atmosphere.

Specifically, when the PCV valve 22 is opened during natural aspiration in which the supercharger 17 is not activated, the atmospheric pressure acts on the intake passage 12 upstream of the throttle valve 18 while the intake negative pressure of the internal combustion engine 11 acts on the intake passage 12 downstream of the throttle valve 18. Hence, the intake air in the intake passage 12 upstream of the throttle valve 18 flows through the breather line 20 into the crankcase 19. From the crankcase 19, the intake air together with the blow-by gas is returned into the intake manifold 14 through the PCV line 21. The blow-by gas together with the intake air is eventually supplied into the combustion chamber of the internal combustion engine 11.

Moreover, at the time of supercharging in which the supercharger 17 is activated, the supercharging pressure acts on the intake passage 12 downstream of the supercharger 17. Once the PCV valve 22 is closed, the supercharging pressure is prevented from escaping through the PCV line 21 into the crankcase 19. The blow-by gas in the crankcase 19 is sucked out into the intake passage 12 by the negative pressure generated upstream of the activated supercharger 17. From the intake passage 12, the blow-by gas together with the intake air is supplied into the combustion chamber of the internal combustion engine 11 through the intake passage 12.

In a case where during the supercharging of the internal combustion engine 11, a first connection portion 23 at which the breather line 20 is connected to the intake passage 12 comes off or a second connection portion 24 at which the breather line 20 is connected to the crankcase 19 comes off, the blow-by gas flowing through the breather line 20 from the crankcase 19 toward the intake passage 12 is possibly released to the atmosphere. For this reason, it is necessary to detect such abnormality of the breather line 20 and issue an alert.

As illustrated in FIG. 2, to an abnormality determination unit 30 formed of an electronic control unit that determines abnormality of the breather line 20, the air flow meter 16 and an alert unit 32 are connected. The alert unit 32 is formed of a liquid crystal panel provided on an instrument panel, for example.

Next, the action of the embodiment including the above-described configuration will be described.

As illustrated in FIG. 3A, a piston 33 of the internal combustion engine 11 is connected to a crankshaft 35 by a connecting rod 34. The height of the piston 33 (the position in the direction of movement of the piston 33) changes as a function of the rotational position of the crankshaft 35 and the oscillation position of the connecting rod 34. That is, the fluctuation in the height of the piston 33 attributable to the rotation of the crankshaft 35 is a rotation first-order fluctuation in which the height fluctuates once per revolution of the crankshaft 35. On the other hand, the fluctuation in the height of piston 33 attributable to the oscillation of the connecting rod 34 is a rotation second-order fluctuation in which the height fluctuates twice per revolution of the crankshaft 35.

As illustrated in FIG. 3B, in the in-line four-cylinder 4-cycle internal combustion engine 11, the pistons 33 of the #1 cylinder and the #4 cylinder operate at the same phase while the pistons 33 of the #2 cylinder and the #3 cylinder operate at a different phase shifted by 180° from the above phase. Hence, the internal pressure fluctuation of the crankcase 19 attributable to the oscillations of the four connecting rods 34 is a rotation second-order fluctuation in which the internal pressure fluctuates twice per revolution of the crankshaft 35.

When the rotation second-order fluctuation is generated in the internal pressure of the crankcase 19 as described above, the pressure fluctuation is transmitted to the intake passage 12 through the breather line 20, causing the rotation second-order fluctuation in the intake flow rate in the intake passage 12. The present embodiment is configured to determine the abnormality of the breather line 20 based on the rotation second-order fluctuation in the intake flow rate generated in the intake passage 12.

Note that the number of cylinders of the internal combustion engine 11 to which the embodiment is applied is not particularly limited. However, in a V-type 6-cylinder internal combustion engine, the pressure fluctuations in the internal pressure of the crankcase 19 due to the movements of 6 pistons 33 cancel out, so that the fluctuations in the internal pressure of the crankcase 19 are relatively small. Hence, the present disclosure is favorably applicable to the in-line four-cylinder internal combustion engine 11.

Next, the procedure of determining the abnormality of the breather line 20 will be described based on FIG. 4.

The determination of the abnormality of the breather line 20 of the present embodiment is executed when the flow rate of the intake air detected by the air flow meter 16 is a predetermined value or more and the internal combustion engine 11 is being operated with a load of a predetermined value or more. This is because when the internal combustion engine 11 is being operated with a small load, the fluctuation in the intake flow rate in the intake passage 12 is small, making it difficult to obtain the amount of fluctuation necessary to determine abnormality with high precision.

First, the fluctuation in the intake flow rate in the intake passage 12 is detected by the air flow meter 16. As described above, a periodic pressure fluctuation is generated in the crankcase 19 by the movement of the piston 33. This periodic pressure fluctuation is transmitted to the intake passage 12 through the breather line 20 connected to the crankcase 19, generating the fluctuation in the intake flow rate. The fluctuation in the intake flow rate in the intake passage 12 contains the rotation first-order component, the rotation second-order component, and rotation third-order and higher-order components. However, since the rotation third-order and higher-order components are small, the rotation first-order component and the rotation second-order component are dominant.

Subsequently, only the rotation second-order component in the fluctuation in the intake flow rate in the intake passage 12 is extracted using a bandpass filter. The principle of the bandpass filter for extracting only the rotation second-order component from the fluctuation in the intake flow rate in the intake passage 12 will be described below.

As illustrated in FIG. 5 ([Math. 1]), if a value obtained by multiplying a certain fluctuation waveform of the intake flow rate in the intake passage 12 detected by the air flow meter 16 by the second-order sine wave is added for each phase, the X component of the rotation second-order component of the certain waveform is obtained. If a value obtained by multiplying the certain waveform by the second-order cosine wave is added for each phase, the Y component of the rotation second-order component of the certain waveform is obtained.

To be more specific, the certain waveform f(t) may be expressed as [Math. 2], summation of sine waves sin(ωt), sin(2ωt), sin(3ωt), . . . and cosine waves cos(ωt), cos(2ωt), cos(3ωt), . . . in accordance with Fourier series expansion. Here, the angular frequency ω has one cycle with 720 deg corresponding to two rotations of the crankshaft 35.

f=1+a ₁ sin(ωt)+b ₁ cos(ωt)+a ₂ sin(2ωt)+b ₂ cos(2ωt)+ . . .   [Math. 2]

When the [Math. 2] is multiplied by the sine wave sin(ωt), followed by integration, only the Fourier coefficient a1 of the angular frequency sine wave is left as shown in [Math. 3].

$\begin{matrix} \begin{matrix} {{\int{f \cdot {\sin \left( {\omega \; t} \right)} \cdot {dt}}} = {\int\left( {1 + {a_{1}{\sin \left( {\omega \; t} \right)}} + {b_{1}{\cos \left( {\omega \; t} \right)}} +} \right.}} \\ {\left. {{a_{2}{\sin \left( {2\; \omega \; t} \right)}} + \ldots} \right) \cdot {\sin \left( {\omega \; t} \right)} \cdot {dt}} \\ {= {\int\left( {{\sin \left( {\omega \; t} \right)} + {a_{1}{{\sin \left( {\omega \; t} \right)} \cdot {\sin \left( {\omega \; t} \right)}}} +} \right.}} \\ {{{b_{1}{{\cos \left( {\omega \; t} \right)} \cdot {\sin \left( {\omega \; t} \right)}}} + {a_{2}{{\sin \left( {2\; \omega \; t} \right)} \cdot}}}} \\ {\left. {{\sin \left( {\omega \; t} \right)} + \ldots}\; \right) \cdot {dt}} \\ {= {{{\int{{\sin \left( {\omega \; t} \right)} \cdot {dt}}}\begin{matrix} {= 0} \\ \; \end{matrix}} + {\int{a_{1}{{\sin \left( {\omega \; t} \right)}^{2} \cdot {dt}}}} +}} \\ {{\begin{matrix} {{\int{b_{1}{{\cos \left( {\omega \; t} \right)} \cdot {\sin \left( {\omega \; t} \right)} \cdot {dt}}}} +} \\ \begin{matrix} {\int{a_{2}{{\sin \left( {2\omega \; t} \right)} \cdot}}} \\ {{{\sin \left( {2\omega \; t} \right)} \cdot {\sin \left( {\omega \; t} \right)} \cdot {dt}} + \ldots} \end{matrix} \end{matrix} = 0}} \\ {= {\pi \; a_{1}}} \end{matrix} & \left\lbrack {{Math}.\mspace{11mu} 3} \right\rbrack \end{matrix}$

Similarly, when the [Math. 2] is multiplied by the cosine wave cos(ωt), followed by integration, only the Fourier coefficient b1 of the angular frequency cosine wave is left. It is thus possible to easily obtain the rotation second-order component of the certain waveform f(t) from these Fourier coefficients a1 and b1.

In FIG. 4, the solid line represents the waveform of the rotation second-order component in fluctuation in the intake flow rate when the breather line 20 is normal while the broken line represents the waveform of the rotation second-order component in fluctuation in the intake flow rate when the breather line 20 is abnormal. When the breather line 20 is normal, the waveform of the rotation second-order component fluctuates in such a manner as to cross the upper threshold and the lower threshold of the intake flow rate. For this reason, a first number of times for which the rotation second-order component exceeds the upper threshold (the number of a points) and a second number of times for which the rotation second-order component falls below the lower threshold (the number of b points) are counted and accumulated. The upper threshold and the lower threshold are both positive values and are set such that the upper threshold>the lower threshold.

Then, the accumulated value of the first number of times and the second number of times is compared with a threshold corresponding to the number of revolutions of the crank. If the accumulated value is equal to or more than the threshold, the breather line 20 is determined to be normal. If the accumulated value is less than the threshold, the breather line 20 is determined to be abnormal and the alert unit 32 is activated to notify a passenger of that effect. When the breather line 20 is normal, the amplitude of the rotation second-order component in the fluctuation in the intake flow rate is sufficiently large. For this reason, each of the first number of times and the second number of times is twice per revolution of the number of revolutions of the crank. Hence, when the number of revolutions of the crank for a predetermined period of time of 2 to 10 seconds for example is denoted by N, the accumulated value of the first number of times and the second number of times is 4N. The threshold is however set to a value slightly smaller than 4N with a detection error taken into account.

The reason why it is possible to determine whether the breather line 20 is normal or abnormal from the accumulated value of the first number of times for which the rotation second-order component in the fluctuation in the intake flow rate exceeds the upper threshold and the second number of times for which the rotation second-order component falls below the lower threshold is as described below. In a case where the breather line 20 is normal and is not in communication with the atmosphere, the pressure fluctuation of the crankcase 19 is transmitted as it is to the intake passage 12 from the breather line 20 and the rotation second-order fluctuation is generated in the intake flow rate in the intake passage 12. Hence, if the fluctuation in the intake flow rate in the intake passage 12 detected by the air flow meter 16 is large, it is possible to determine that the breather line 20 is not in communication with the atmosphere and is normal. On the other hand, if the breather line 20 has come off the first or second connection portion 23 or 24 or is broken in a middle thereof, the breather line 20 communicates with the atmosphere and the fluctuation in the intake flow rate in the intake passage 12 is reduced. Hence, if the detected fluctuation in the intake flow rate is small, it is possible to determine that the breather line 20 is in communication with the atmosphere and is abnormal.

Meanwhile, consider a case where the magnitude of the fluctuation in the intake flow rate in the intake passage 12 is evaluated. If the intake flow rate fluctuates to a positive value and a negative value, merely accumulating the intake flow rate over a predetermined period of time results in incorrect evaluation because the positive and negative values cancel out. In view of this, as in the present embodiment, using the accumulated value of the first number of times for which the rotation second-order component in the fluctuation in the intake flow rate exceeds the upper threshold and the second number of times for which the rotation second-order component falls below the lower threshold makes it possible to correctly evaluate the magnitude of the fluctuation in the intake flow rate and conduct the abnormality determination with high precision.

In addition, if the load on the internal combustion engine 11 fluctuates due to disturbance or the like, the rotation first-order component of the fluctuation in the intake flow rate in the intake passage 12 also fluctuates. However, since the rotation second-order component is hardly affected, it is possible to increase the determination precision and prevent erroneous determination from occurring by conducting the abnormality determination on the breather line 20 base on the rotation second-order component.

Although the embodiment of the disclosure has been described so far, various modifications in design may be made without departing from the scope of the disclosure.

For example, the number of cylinders of the internal combustion engine 11 is not limited to the four in the embodiment.

Moreover, although the breather line 20 is connected to the crankcase 19 in the embodiment, it is also possible to achieve the advantageous effect of the disclosure by causing the internal space of the crankcase 19 and the internal space of a head cover to communicate and connecting the breather line 20 to the head cover. Hence, an embodiment in which the breather line 20 is connected to another space that communicates with the crankcase 19 is also encompassed by the scope of the disclosure.

In addition, in the embodiment, the first number of times for which the rotation second-order component in the fluctuation in the intake flow rate exceeds the upper threshold and the second number of times for which the rotation second-order component falls below the lower threshold are combined and accumulated. However, it is possible to employ a configuration that the first number of times and the second number of times are separately accumulated, and if both the accumulated value of the first number of times and the accumulated value of the second number of times are less than thresholds, the abnormality is determined. Although a specific form of embodiment has been described above and illustrated in the accompanying drawings in order to be more clearly understood, the above description is made by way of example and not as limiting the scope of the invention defined by the accompanying claims. The scope of the invention is to be determined by the accompanying claims. Various modifications apparent to one of ordinary skill in the art could be made without departing from the scope of the invention. The accompanying claims cover such modifications. 

What is claimed is:
 1. An abnormality determination apparatus of an internal combustion engine in which an intake passage located upstream of a forced-induction system and a crankcase are connected by a breather line, comprising: an intake flow rate detection detector that detects an intake flow rate in the intake passage; and an abnormality determination unit that determines abnormality of the breather line, wherein the abnormality determination unit: calculates a rotation second-order component of a fluctuation waveform of the intake flow rate, accumulates a first number of times for which the rotation second-order component exceeds an upper threshold and a second number of times for which the rotation second-order component falls below a lower threshold to obtain an accumulated value of the first number of times and the second number of times, and determines occurrence of the abnormality of the breather line by comparing the accumulated value of the first number of times and the second number of times with the number of revolutions of a crank of the engine.
 2. The abnormality determination apparatus of an internal combustion engine according to claim 1, wherein the rotation second-order component is calculated by multiplying the fluctuation waveform of the intake flow rate by a sine wave and a cosine wave corresponding to an angular velocity of the crank of the engine, followed by integration.
 3. The abnormality determination apparatus of an internal combustion engine according to claim 1, wherein the abnormality determination unit determines occurrence of the abnormality of the breather line when the accumulated value is lower than a threshold which is correlated with the number of revolutions of the crank of the engine.
 4. The abnormality determination apparatus of an internal combustion engine according to claim 1, wherein the abnormality determination unit accumulates the first number of times for which the rotation second-order component exceeds the upper threshold and the second number of times for which the rotation second-order component falls below the lower threshold for a predetermined rotation period of the crank, and obtains the number of revolutions of the crank during the predetermined rotation period.
 5. The abnormality determination apparatus of an internal combustion engine according to claim 1, wherein the rotation second-order component represents a rotation second-order fluctuation generated in an internal pressure of the crankcase.
 6. An abnormality determination method of an internal combustion engine in which an intake passage located upstream of a forced-induction system and a crankcase are connected by a breather line, the method comprising steps of: detecting by an intake flow rate detection detector an intake flow rate in the intake passage; calculating by a computer a rotation second-order component of a fluctuation waveform of the intake flow rate; accumulating by the computer a first number of times for which the rotation second-order component exceeds an upper threshold and a second number of times for which the rotation second-order component falls below a lower threshold to obtain an accumulated value of the first number of times and the second number of times; and determining by the computer occurrence of the abnormality of the breather line by comparing the accumulated value of the first number of times and the second number of times with the number of revolutions of a crank of the engine. 